Composite laminates of textile materials, for example, often include a barrier film to prevent the passage of liquids and gases through the laminate. In addition to the barrier film, these barrier laminates include other layers such as foams, fabrics, nonwovens, and breathable films.
Examples of barrier laminates include waterproof breathable laminates, breathable chemical protection laminates, viral protection laminates, mold-in-place laminates, and allergy proof and fluid proof laminates. Generally these laminates are manufactured by using heat, pressure and/or adhesives to adhere layers of the laminate together.
To function properly as a barrier, these laminates generally must be non-porous, i.e., free of even small holes. For example, to form a fabric-covered seat cushion, a barrier laminate may be vacuum drawn into a female tool, e.g., at a vacuum of about 15-25 inches of water, and a foaming liquid applied to the exposed surface of the laminate. In this case, a large pressure differential is applied to the laminate, and as a result the foaming liquid may penetrate even very tiny holes, potentially resulting in an unacceptable product. Similarly, in low pressure injection molding, a barrier laminate may be laid into a mold and a thermoplastic injected into the mold at a pressure that forces the laminate against the mold surface. In this case, the positive pressure exerted by the plastic may force plastic through even tiny holes in the laminate.
A variety of tests have been used to check laminates for small holes. Generally, testing is performed off-line on samples of the laminate. In some off-line tests a liquid is applied to one side of the sample and a vacuum is drawn on the opposite side. Because testing is performed off-line, there is typically a time-lag between production and testing, which may result in large quantities of defective laminate being manufactured before a problem is identified.